Arc extinguishing material



R. H. AMuNDsoN Erm. 2,526,448

ARC EXTINGUISHING MATERIAL Oct. 17,'1950 Filed Aug. 25, k1949.

.lill/lill illy lalaa..

Patented Oct. 17,' 1950 ARC EXTINGUISHIN G MATERIAL Roald H. Amundson and Henry V. Dryer, Milwaukee, Wis., assignors to McGraw Electric Company, a corporation of Delaware Application August 25, 1949, Serial No. 112,378

v 12 Claims.

l The present invention relates to electrical devices in which an arc may be generated by excessively high current or voltages and more particularly to an arc extinguishing material contained within such devices capable of evolving gases which smother the arc and thereby quickly and effectively break the circuit.

Many different types of compositions have been suggested for use as arc extinguishing material in high voltage fuses, circuit breakers, lightning arresters, and the like. One of the common arc extinguishing materials in use today is boric acid, which decomposes under the conditions of the arc to generate water vapor and to leave a deposit of boron oxide. The water vapor generated serves as an arc extinguishing gas.

In addition to boric acid, various other arc extinguishing materials, such as fiber, and resins such as phenolic resins and aminoplast resins sometimes find use as arc extinguishers. These resins have the disadvantage of frequently being incapable of generating a suillcient volume of arc extinguishing gas to extinguish the arc completely.

A good arc extinguishing material must be capable of generating a large volume of non' combustible gas within a short time after the arc has been struck. In addition, the material and its solid residue in a fused state must be relatively non-conductive so as to prevent restriking of the arc by conductance through the fused compound. In addition, the arc extinguishing material must be relatively insoluble in water so that it will not be affected by moisture present in the atmosphere. In addition, the arc extinguishing material should have the property of being molded into a self-sustaining mass without large amounts of inert binders.

An object of the present invention, therefore, is to provide electrical devices in which an arc may be generated by excessively high currents or voltages and means within the arcing areas which are decomposable by the heat of the arc to generate large volumes of essentially noncombustible gases capable of quickly extinguishing the arc.

Another object of the present invention is to provide arc extinguishing material having the property of negligible electrical conductivity in the fused state to thereby avoid restriking the arc after the arc has once been extinguished by the generated gases.

A further object of the present invention is to provide arc extinguishing material which is easily molded into a self-sustaining structure.

Another object of the invention is to provide material which is relatively resistant to atmosv pheric conditions and which may be used in 2 e installations which are normally subject to the effects of climatic conditions.

We have now found that arcs generated by excessively high currents or voltages may be completely and effectively extinguished where the arcing area is provided with a specific type of heterocyclic nitrogen compound. In particular, the material contemplated by the present invention may be most conveniently expressed as monomeric compounds which contain a single 1,3,5-triazine group. structurally, each of these compounds contains the following carbonnitrogen arrangement:

By the term monomeric as used in the specification we mean those compounds each molecule of which has only a single group of the type indicated; that is, compounds that have not been polymerized nor reslnified with condensation agents. The latter types of compounds contain a plurality of reactive groups interlinked by carbon and oxygen linkages. pounds have been found to be substantially less effective for this purpose than the monomeric compound.

The basic reactive group shown above may be substituted with many different kinds of substituents, without impairing the effectiveness of the resulting compound as an arc extinguishing medium. Thus, one of the better arc extinguishing medium containing the above-noted reactive group is the triamino substituted 1,3,5 triazine commonly known as melamine. This compound has the following formula:

replaced by an acetyl group, the resulting compound, acetoguanamine, is also a very effective arc extinguishing material. This compound has the formula:

CocHx HiN-C (IJ-NH: \N%

Such types of com- Benzoguanamine, another very effective arc extinguishing material, has the formula:

N N t HzN- c-Nm N The thio-substituted derivatives are also effective for this purpose. A typical example of one such compound is dithioammelide having a structural formula as follows:

N/ Il Hs-c C-su Ammeline, another effective compound, has the following structure:

THe

Where each of the 1,3,5 triazine groups are substituted with halogen atoms, a compound such as `icyanuric chloride is produced. This compound has the following structure:

II Cl-V All of the above-noted compounds have the ability to generate large volumes of arc extinguishing gases under the influence of an electric arc. These gases contain components such as carbon dioxide, nitrogen, and oxides of nitrogen all of which are essentially non-inliammable so that they quickly and effectively extinguish the existing arcs. In addition, all of the above compounds, both before and after decomposition, show practically negligible conductivity in the fused state and consequently do not have a tendency to permit restriking of the arc after it has once been extinguished.

The extinguishing action is also very rapid, the circuit being cleared within a half cycle of the impressed frequency after initiation of the arc.

A further description of the present invention will be made in connection with the attached sheet of drawings which will illustrate one preferred embodiment of the arc extinguishing material as used in a high voltage fuse assembly. It will be appreciated that the material herein described is useful in other types of electrical devices wherein arcs are encountered, for example, in lightning arresters, circuit breakers, and cable installations.

On the drawings:

Figure l shows a fragmentary cross-sectional view of a high voltage fuse assembly containing 4 a fusible link associated with arc extinguishing material; and

Figure 2 is a view taken substantially along the line H-l of Figure 1.

As shown on the drawings:

Reference numeral IU denotes generally a high voltage fuse assembly formed into an outer cylinder I I which is preferably composed of a resinous material such as a phenolic resin of the Bakelite type. A metallic ferrule l2 surrounds one end of the cylinder I I and is held thereon by means of pins I3 and I4 to complete the supporting structure for the replaceable fuse unit.

The replaceable unit includes an intermediate sleeve I5 which is freely movable within the interior of the outer cylinder II and is threaded at one end into an end portion I6 of the fuse I0 and seated against a collar Il, secured in the assembly by means of the pins I8. The end portion IS is secured within the sleeve I2 by means of a locking collar 29 threaded onto the ferrule I2 and seated against an annular shoulder 30 of the end portion I6.

A fuse link button I9 formed into a flange portion 20 is disposed Within the end portion I6, with the flange portion 20 overlying the ends thereof. Secured to the button I9 is a strain wire 2l and a fusible link 22. The opposite ends of the strain wire 2I and of the fusible link 22 are secured to one end of a rod 23, The opposite end of the rod 23 is held by means of connector 24 to a tensioned conducting lead 25.

Around the fusible link 22 there is provided a collar 26 which is, suitably composed of heat and f arc resistant material.

When the link 22 is broken by an excessively high current, an arc will be struck between the end of the button I9 and the retreating end of the rod 23 as it is pulled out of the assembly under the action of the tensioning force applied to the connector 24. To extinguish the resulting arc and thus clear a circuit at the earliest possible time, there is provided an arc extinguishing structure consisting of a series of molded blocks 21 of an arc extinguishing compound of the type herein noted above. The blocks 21 are disposed about a major portion of the rod 23 and in effect surround the path of the arc drawn between thc button I 9 and the rod 23. A restraining collar 28, which may consist of fiber, is provided at one end of the block assembly and is threaded into the intermediate sleeve I5.

VV hen the fuse has blown, the fuse elements may be replaced by unscrewing cap 29, removing the end portion I6 and the elements contained within the intermediate sleeve I5, and replacing the same with a new cartridge.

While the drawing illustrates the arc extinguishing material in the form of hollow cylindrical blocks, the arcing area may also be provided with e. single hollow cylinder composed of the arc extinguishingr material, or the compound may be applied to the surface of another arc extinguishing medium such as ber or a phenolic resin.

'I'he compounds of the present invention are easily molded in suitable dies to a self-sustaining structure, but, in addition, small amounts of plaster of Paris, normally from l0 to 20%, may be incorporated into the composition to act as a rigidifying medium.

As previously described, the compounds of the present invention show practically negligible conductivity in their fused state. In making conductivity tests, the compound to be tested was fused and a pair of electrodes were inserted into the fused mass. An alternating current voltage of 240 volts was thereupon impressed and current readings taken by means'of a milliameter. Under these conditions, all of the compounds showed a conductivity of less than one milliampere and in most cases the current was not even suilicient to register on the milliameter.

The eiiicacy of the substances as arc extinguishers was determined by positioning two stationary electrodes with a fusible link between the electrodes and determining the length of material necessary to extinguish the arc created by the failure of the fuse under overloadconditions. The usefulness of the material as an arc extinguisher is inversely proportional to the length of material necessary to extinguish the arc.

Under the test conditions mentioned above. a block of borc acid oneand one-half inches in length was necessary to extinguish the arc. When using melamine, a length of only threequarter inch was required, and, when using acetoguanamine and benzoguanamine. the length required was one and one-quarter inches.

From the foregoing, it will be apparent that we have herein provided arc extinguishing material capable of completely and effectively extinguishing arc caused by current overloads in electrical systems. The materials of the present invention are no n-conductive in the fused state so that there is no possibility of restriking the arc by conduction through the fused material after the initial arc has been extinguished. In addition, the materials are capable of being molded into a self-sustaining structure not aiected by atmospheric conditions to any substantial degree. y

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

We claim as our invention:

1. An electrical circuit comprising means for forming an arc, and means along the path of the arev capable of evolving an arc extinguishing gas and comprising a monomeric compound containing a 1,3,5 triazine group.

2. An electrical circuit comprising means for formingan arc, and means along the path of the arc capable of evolving an arc extinguishing gas and comprising monomeric melamine.

3. An electrical circuit comprising means for forming an arc, and means along the path of the arc capable of evolving an arc extinguishing gas and comprising monomeric acetoguanamine.

4. An electrical circuit comprising means for forming an arc, and means along the path of 6 the arc capable of yevolving an arc extinguishing gas and comprising monomeric benzoguanamine.

5. A fuse assembly comprising a fusible link and an arc extinguishing material associated therewith capable of evolving arc extinguishing gases in the presence of an arc and comprising a monomeric compound containing a 1,3,5 triazine group.

6. A fuse assembly comprising a fusible link and an arc extinguishing material associated therewith capable of evolving arc extinguishing gases in the presence of an arc and comprising monomeric melamine.

7. A fuse assembly comprising a fusible link and an arc extinguishing material associated therewith capable of evolving arc extinguishing gases in the presence of an arc and comprising monomeric acetoguanamine'.

8. A fuse assembly comprising a fusible link and an arc extinguishing material associated therewith capable of evolving arc extinguishing gases in the presence of an arc and comprising monomeric benzoguanamine.

9. A fuse having a fusible link and a molded arc extinguishing material disposed along the path of the arc drawn by melting of the link, and comprising a compound containing a single 1,3,5 triazine group.

l0. A fuse having a fusible link and hollow cylindrical blocks of an arc extinguishing material disposed along the path of the arc drawn upon melting of the fusible link, said blocks consisting of a molded compound containing a single 1,3,5 triazine group.

11. An electrical circuit comprising means for forming an arc, and means along the path of the arc capable of evolving an arc extinguishing gas and comprising monomeric dithioammelide.

12. Anv electrical circuit comprising means for forming an arc, and means along the path of the arc capable of evolving an arc extinguishing gas land comprising monomeric ammeline.

ROALD H. AMUNDSON. HENRY V. DRYER.

REFERENCES CITED The following references are of record in the le of this patent: 

